Pythium vexans causing stem rot of Dendrobium in Yunnan Province, China.

摘要

Since 2002 a severe root and stem disease of Dendrobium has occurred periodically each year in the plantations of Simao City, Yunnan Province, China. Symptoms included water-soaked and brown lesions, and rot of tissues. Based on the morphological characteristics and the internal transcribed spacer-1, 5.8 S ribosomal RNA gene, and internal transcribed spacer 2 and beta -tubulin gene sequences, the pathogen was identified as Pythium vexans de Bary. The pathogenicity of the fungus was confirmed by satisfying Koch's postulates. This is the first world record of stem rot of Dendrobium caused by P. vexans.